"It's ... difficult to get an absolute answer about just what is, or isn't, in Delaware's water -- difficult enough that some real estate agents routinely suggest water-filter installations even in the absence of known problems.
Although most residents are supplied by regularly tested public drinking water systems, thousands of unregulated substances can be found in the environment and water. Thousands of homes, meanwhile, take water directly from the ground, with testing left up to the owners.
Testing is a critical routine for most of the state's water suppliers. Filtering is ubiquitous."
Jeff Montgomery reports for the Wilmington News Journal July 25, 2010.